Whilst there's only two waves per year, there's usually a few more exclusives released later in the year. For instance, in 2007, these exclusives were the Hoth Rebel Base and the Republic Cruiser, and they were released in the Autumn. In 2008, the late sets were the Twilight and the Spider Droid.
The mid-scale Falcon and the Pirate Tank are 2009 sets, and will be released later this year. They will most likely be exclusives as well.

I've just merged this with the new topic. (I accidentally merged it the wrong way around, so that this thread was moved into the Culture forum ).
Anyway, enjoy the new pics of the Mon Calamari Cruiser set!
EDIT: First post edited with new pics.

I remember a few years ago TLC made a poll so that AFOLs could vote for the set they wanted. There were about eight sets listed if I remember correctly. By the end of the next year, every set on the list had been released.